In general, it is either substantive dyes or oxidation dyes which are used for coloring keratinic fibers. Although intense and sustained colorings may be achieved with oxidation dyes, the color generally develops under the influence of oxidizing agents such as for example H2O2, which may in some cases result in damage to the fibers. Moreover, some oxidation dye precursors or certain mixtures of oxidation dye precursors may have a sensitizing effect in people with sensitive skin. Substantive dyes are applied under milder conditions. The disadvantage thereof, however, is that the colorings frequently are not sustained as long as those produced from oxidation dyes, in particular when the hair is washed, but also in relation to external influences, such as sunlight or reactive environmental chemicals, such as for example swimming pool water.
One particular challenge for hair coloring using substantive dyes is uniformly coloring frequently pretreated hair, such as for example bleached or permed hair, in which the fibers have highly variable levels of prior damage at different lengths or in differently treated areas. During the actual coloring, the coloring agent may exhibit uneven coloring behavior on hair suffering differing levels of prior damage, but repeated hair washing can also wash out the dyes to varying extents in the different areas of hair, leading to a non-uniform and thus unwanted coloring result.
It is therefore desirable to provide coloring agents for keratinic fibers, in particular human hair, which exhibit good applicational properties with regard to color depth and fastness characteristics, such as in particular light, abrasion and washing fastness as well as sweat and cold perming fastness. Finally, it is particularly desirable to provide coloring agents with a good equalizing capacity.
If keratinic fibers are to be oxidatively lightened or blonded, substantive dyes may also be used in combination with oxidizing agents. Hair is generally blonded by applying aqueous hydrogen peroxide solutions, either alone or in combination with further oxidizing agents acting as bleach activators such as for example persulfate salts, onto the keratin fibers. In order to achieve a sufficient blonding action, such agents are conventionally strongly alkalized, the pH generally being between 9 and 10.5. Under the action of the oxidizing agents, the melanins, the natural, color-imparting pigments of hair fibers, are oxidatively destroyed and the fibers are consequently decolorized or lightened. Melanins are located in the cortex of the hair fibers and may be divided into two classes of pigments. Eumelanins are the first, brownish-black class of pigments, while the reddish pigments with a higher sulfur content are known as pheomelanins. Due to the different levels of resistance of the various types of pigment to oxidizing agents, the pheomelanins and eumelanins are, however, not always uniformly decolorized. In addition, in darker hair with an elevated melanin content, the melanins may only be partially or incompletely broken down and therefore a residual proportion of the color-imparting pigments remains in the hair after blonding. In these cases, the residual content of melanins still present in the hair after the oxidative process results in a yellowish to reddish shift in shade. Therefore, in particular when blonding darker hair, a color shift towards warm tints occurs.
Users do not normally desire such color shifts towards warm tints. This color shift is therefore usually counteracted by tinting in the corresponding complementary color according to color theory. The aim here is to achieve a silvery cool appearance of the bleaching result. A person skilled in the art refers to this as matting. Blue substantive dyes may in particular be used for matting blond shades with an orange cast. In order to ensure the completest possible attenuation of the orange color appearance, it is advantageous for the blue dye itself to have no red content in its coloring. Dyes in pure blue and in particular in grayish blue shades are thus better suited to matting an orange blonding result than are blue dyes with a violet cast. However, despite the numerous blue dyes usable in hair coloring products, no dyes are known from the prior art which optimally meet all the above-stated requirements. There is accordingly still a major need for novel substantive dyes with corresponding coloring and matting properties.
GB 1 053 300 describes a process for coloring hair in which 1,4-diaminoanthraquinone derivatives may be used which bear one or two dialkylaminoalkyl substituents on the amino groups thereof. These dyes are intended to have a good coloring capacity, elevated water solubility and elevated lightfastness. The range of shades extends from intense blue via blue-violet to mauve, pink and blue-green. Blue colorings with a gray cast cannot, however, be obtained by means of these dyes. DE 1 644 306 discloses a method for producing 1,4-diaminoanthraquinone derivatives which bear an aminoalkylamino substituent on each of the two nitrogen atoms of the anthraquinone ring. The dyes produced in the context of this method are intended to have an elevated affinity for keratin fibers and good washing fastness. The range of shades achieved with the dyes extends from yellow to blue. Blue color shades with a gray shift cannot be achieved with these derivatives either.
It is particularly desirable to find novel matting dyes which meet the conventional fastness requirements placed on substantive dyes, have good storage stability and furthermore have a blue color shade tending strongly towards grayish without any red content. It is intended to be possible to use the dyes not only in the form of a post-treatment after the oxidative blonding process but, in single-stage methods, also simultaneously with the oxidizing agent, for which reason they must additionally have good stability towards the oxidizing agents.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.